1. Field of the Invention
The present invention relates to a new and improved lubricated split plug valve that may be used on high pressure fluid lines to control the flow therethrough.
2. Description of the Prior Art
The prior art valve often recommended for heating and other treating units, gathering systems, recycling and gasoline plants, blow out preventers and other applications wherein the flow of high pressure working fluid in the range of 3,000 to 6,000 psig is controlled is a lubricated plug valve. An example of such a typical prior art valve is illustrated in U.S. Pat. No. 2,269,887 and this patent is incorporated by reference herein. Prior art valves of the type employed in systems wherein substantial pressures are controlled use valve plugs that tend to be forced against the downstream seal in the valve body resulting in the valve plug being virtually impossible to open without injecting a lubricant or sealant.
One approach to overcoming this problem in the prior art is illustrated in U.S. Pat. No. 2,269,887. This valve utilizes mating lubricating and seal grooves fabricated in both the outer peripheral surface of the valve plug and the inner peripheral surface of the valve body. In this way, overlapping communicating grooves completely encircle the downstream port in the closed position thereby allowing access of lubrication and reducing the torque required to close the valve.
These typical prior art valves, however, require correct alignment of a groove on the outer peripheral surface of the valve plug and a groove defined on the inner peripheral surface of the valve body and continuous flow of lubricant from the first groove to the second groove to ensure the desired complete lubrication. This alignment occurs only in the closed position of the plug. Due to the pressures forcing the lubricant through these grooves and the difficulty of alignment of the grooves, there is a substantial pressure drop resulting in incomplete lubrication. In addition, the high pressure fluid flowing around the valve plug tends to wash the lubricant out of these grooves defeating the purpose of the lubricating system in the typical prior art valve.
A further problem with the typical prior art valves of the type illustrated in U.S. Pat. No. 2,269,887 is that a reservoir is included in the valve body to supply lubricant to the grooves. The reservoir includes a plunger that is placed under downstream line pressure to act against lubricant forcing it into the groove; however, over a period of time, gravity acts on the plunger in a manner to create voids between the plunger and the lubricant within the reservoir resulting in inadequate lubrication even while the valve is closed. Consequently, before opening or closing the prior art valve, pressurized lubricant must be forced into the reservoir to increase the pressure to the desired level and obtain lubrication.